Yep, this is why I stated in my prior posting that if Ford had designed the PCV valve control section in the DS valve cover to be serviceable then the only item needed would have been to swap out the PCV valve plunger w\ another 1 that has a smaller orifice or use something to plug the existing orifice in the plunger & drill a smaller one to replace it that would have served the same purpose but would open up fully on lowered manifold vacuum signal (normal operation of a PCV valve) thus why I also said in prior posting that a 2nd PCV valve is what is needed w\ a smaller orifice but no one makes 1 that is designed to be taken apart to resize the orifice so this UPR check valve is the only device that I could find that is metal, easily serviceable (can be taken apart & reassembled easily) & uses a sliding plunger type Teflon seat. The spring inside this check valve is not that strong & will easily allow the plunger to move off it's seat w\ a very small vacuum applied but I tested this as well by installing varying amounts of shimming then testing to see how much effort it would take to unseat it & as long as I didn't exceed 2 washer's thickness I could easily unseat the plunger off it's seat & move air thru the 1/8" orifice. In reality probably only needed to use 1 washer anyway......
The main issue as you've noted is whether enough of a vacuum signal still exists at WOT & high RPM's (created from deltaP thru the TB venturi's w\ butterfly blades fully open but I'm not sure if the TB TPS sensor is designed to go to a full 100% open range so the TB blades may be opened to only 86% max....Ford Workshop Manual states that at 96% duty cycle which is max for S197 ETC the TB blades are at 86% actual max open angle...any ETC duty cycle % signal past 96% will trigger limp mode) to keep up w\ the amount of cylinder blow by produced thru this 1\8" orifice since it is a fixed orifice. Using this setup w\ a NA engine I don't foresee an issue since the cylinders are operating within the OEM designed CR index unless this index is changed (by increasing the cylinder CR) or the engine's cylinder walls & piston rings are so worn out creating excessive amounts of blow by gasses. I actually thought about testing for this but to do so I would have to rig up a test port to attach a vacuum gauge upstream of this device to measure the amount of vacuum drop but what would really be needed is an airflow metering device installed to actually measure the amount of actual air volume flow thru PCV system at WOT....which I ain't got so if the FWM data is correct (I can't see why Ford would output bad data in this manual) then there should still be more than enough of a vacuum signal created at high RPM's from the TB plates being less than full open to properly evacuate the CC....even thru this 1/8" orifice...in a NA engine (you'd be surprised at how much actual air volume can be moved thru a small orifice due to the compressibility factor index of air at low deltaP across the orifice due to the gas composition % of the total air stream & if any hydrocarbons (gasses lighter than air) are mixed w\ the air stream this INCREASES the air's compressibility index so can move even more volume at the same deltaP). In addition the PCM will be retarding the cam timing according to the WOT VCT tables which will lower engine dynamic compression at high RPM's thus lower cylinder pressure thus lower potential blow by gasses as well in a NA engine....by design unless a tuner resets the settings in the tune to stop this from happening but I think you'll not appreciate the mid/upper range HP\TQ losses from doing that...……what VCT brought to the overall performance curve of these 3V engines & IMHO shouldn't be disabled if engine usage will involve daily normal street operation…...
Now when talking FI (Roots\TVS blowers only as they still incorporate the full OEM PCV flow design process, centri's & turbos will REQUIRE a check valve to block the DS PCV route off when under boost so CC blow by gasses will revert back thru the PS valve cover anyway) this isn't needed as the Roots/TVS blower is drawing so much more air volume flow thru the CAI\TB intake tract the existing PCV plunger's orifice may not be big enough as the PCV plunger may still be drawn onto it's seat at high RPM's w\ WOT due to high PCV system vacuum thus air flow (especially if the smaller 55mm TB is still being used) thus causing any extra CC blow by gasses to actually revert back thru the PS side valve cover into the CAI upstream of the TB. Most likely is why most FI users have catch cans installed on both sides of the PCV system...…...also why some remove the PCV valve plunger in the DS valve cover as well..…….
Anyway I drove the car today (was too lazy to do it yesterday...….) to test operation under actual driving conditions & can report that all throttle deceleration control has returned to normal w\ this 62mm TB...even w\ car still in motion w\ TB closed & clutch engaged\disengaged. The PCV system flow is now controlled to the point that the MAF signal is now fully & completely following the TB blade angle so the PCM is metering fuel to match so engine will now properly slow down to set idle RPM speed once the injectors are turned back on after engine RPM's drop below 1,000 RPM's on deceleration w\ 62mm TB in full closed position (foot off accel pedal). Prior to this device being installed the engine RPM's would hold at the 1,000 RPM mark while slowing down w\ TB in closed position until car was fully stopped (clutch pedal engaged) at which time the PCM would then pull TB blades to drop the MAF signal to lower engine RPM's to idle set speeds then cut fuel to match the MAF which would cause the engine idle to drop below 700 then PCM would correct back up to the set idle speed. This was due to the excess air volume flow after MAF section bypassing the 62mm TB thru the PCV system. I "fixed" this prior by keeping the engine engaged to the drive train when decelerating using the brakes to slow the engine RPM's down to idle speed then engaging the clutch to stop as the MAF signal will follow the engine RPM's thus the PCM will meter fuel accordingly.
I don't have to do this anymore since installing this device. The 1/8" orifice may actually be overkill to rectify this issue meaning a larger orifice than this 1/8" can solve this issue as well but if I don't find any operational conditions to warrant resizing or removal it's a done deal. The 1 major issue that I can see occurring is potential orifice hydrate (freeze off) in cold weather depending upon conditions until under hood temps rise enough to counter it (tis why some external PCV valves are either coolant heated using engine jacket coolant or electric heated on some make's engine designs....also 1 of the reasons why Ford designed the PCV valve assembly to be a permanent internal design inside the valve cover, FYI).
I'll find this out in a few months as the weather's changing already up here in the Four Corners area...……...